Jarring Apparatus

ABSTRACT

A downhole jarring apparatus for use in jarring an object in a bore comprises a first jarring portion including a first impact surface and a second jarring portion including a second impact surface. The apparatus includes a rotatable jarring arrangement operable to translate a rotational drive movement to cause relative axial movement of the first and second impact surfaces to establish axial impact therebetween.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Divisional application of U.S. application Ser.No. 14/778,428, filed Sep. 18, 2015, which is a National Phase ofPCT/GB2014/051212, filed Apr. 17, 2014; which claims priority under 35U.S.C. § 119 to Great Britain Application No. 13071121, filed on Apr.19, 2013, in the Great Britain Property Office (GBPO), the entirecontents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a jarring apparatus for use in jarringan object within a bore, such as a wellbore.

BACKGROUND TO THE INVENTION

Many industries require objects such as tools to be deployed throughbores, such as wellbores in the oil and gas exploration and productionindustries, and there is always the risk of such objects becoming stuckin the bore. For example, wellbores may be drilled into the earth usinglong drill strings, which may become stuck, for example due tofrictional engagement with the bore wall, due to collapse of the bore,due to differential pressures between the bore and surrounding formationpushing the drill string against a bore wall, due to binding with drillcuttings, or the like. Successful recovery of the drill string is ofextreme importance and value to a drilling operator as the cost offailure to recover the tools and the well could run into several tens ofmillions of pounds.

Current methods for recovering stuck objects include impact tools knownas jars which function to hammer or jar a stuck object. Drilling jarsare universally employed globally by companies in the drilling andconstruction of oil and gas wells. However, current jarring technologyhas not changed or evolved for several decades, and is extremely limitedin its functionality. For example, existing jarring tools may beconsidered to be slow, imprecise, hazardous, costly and damagingly largescale and slow rate.

Generally, a drilling jar is a mechanical device used downhole todeliver an impact load to another downhole component such as a bottomhole assembly (BHA). Known drilling jars operate by storing energy in adrilling string, for example by applying tension within the string, andsuddenly releasing this energy to cause two impact surfaces to moveaxially and strike each other, creating an impact or jarring forcewithin the drill string. This conventional drilling jar technology isknown as a ‘Linear Jarring’ method and offers limited functionality andpresents several significant drawbacks during its operation, such as:

-   -   Each impact has a high recoil force which reverberates back to        the rig, shaking and impacting the rig derrick and        superstructure detrimentally.    -   Time between impacts is lengthy—up to 2 minutes between impacts.    -   The inability to readily adjust the magnitude of a generated        jarring force, as this is conventionally set at a predetermined        value prior to the drilling jar being deployed.    -   Re-setting of the jar between impacts requires a force to be        applied to the jar and drill-string in the opposite direction,        consequently pushing the stuck drill-string back into the        problem portion of the well.    -   High amplitude/low frequency jarring (large impact force with        long intervals between impacts, which is a feature of linear        jarring) is often the cause of further hole collapse and can add        to the problem which is trying to be resolved.    -   High amplitude/low frequency impact performs poorly in freeing        stuck pipe in clays and shales, which are a common rock type to        cause sticking of pipe and hole instability.    -   High amplitude/low frequency jarring performs poorly in        addressing stick-slip binding of a drill string, in which a        single jar only achieves a small slipping motion before the        drill string sticks again.

Various drilling jarring tools and methods are disclosed in, forexample, U.S. Pat. No. 7,882,906, U.S. Pat. No. 3,199,933, U.S. Pat. No.1,653,093, U.S. Pat. No. 1,653,094, U.S. Pat. No. 1,901,513, U.S. Pat.No. 2,146,454, U.S. Pat. No. 2,153,883, U.S. Pat. No. 3,139,933, U.S.Pat. No. 4,890,682, U.S. Pat. No. 7,191,852, U.S. Pat. No. 4,576,229, WO2009/134886 and U.S. Pat. No. 6,845,818.

SUMMARY OF THE INVENTION

An aspect of the present invention relates to a downhole jarringapparatus for use in jarring an object in a bore.

The apparatus may comprise an impact arrangement comprising opposingimpact surfaces. The apparatus may comprise a rotatable jarringarrangement which is operable to translate a rotational drive movementto cause axial impact between the impact surfaces.

The apparatus may comprise multiple impact arrangements each comprisingopposing impact surfaces. The impact arrangements may be operablesimultaneously. The impact arrangements may be operable independently ofeach other.

According to an aspect of the present invention there is provided adownhole jarring apparatus for use in jarring an object in a bore,comprising:

a first impact surface;

a second impact surface; and

a rotatable jarring arrangement operable to translate a rotational drivemovement to cause relative axial movement of the first and second impactsurfaces to establish axial impact therebetween.

In use, the apparatus may be engaged with an object, such as an objectwhich has become stuck in a bore, and the first and second impactsurfaces axially impacted together by operation of the rotatable jarringarrangement, thereby applying a jarring effect to the object. As thisjarring effect is achieved by a rotational drive movement, the apparatusmay be defined as a rotary jarring apparatus. Furthermore, as thisjarring effect is achieved by a rotational drive movement, rather than asolely relative linear motion, problems associated with prior art linearjars may be at least partially addressed.

The first impact surface may be provided on a first jarring portion, andthe second impact surface may be provided on a second jarring portion.The rotatable jarring arrangement may be associated with at least one ofthe first and second jarring arrangements.

The apparatus may be configured to assist in freeing a stuck object topermit removal of the object from the bore, and/or to permit furtheradvancement of the object through the bore.

The apparatus may be configured to actuate or operate an object within abore. For example, jarring of an object by the apparatus may cause theobject to be actuated.

The apparatus may be configured for use within any suitable bore. In oneembodiment the apparatus may be configured for use within a drilledbore, such as a drilled wellbore extending into the earth, for exampleto extend to a subterranean formation. The apparatus may be configuredfor use within an open or unlined drilled bore. The apparatus may beconfigured for use within a bore which is in the process of beingdrilled. The apparatus may be configured for use within the bore of atubing structure, such as within a casing or liner tubing structurewhich lines a drilled bore, within a pipe-line, such as a surface orsub-surface pipe-line, or the like.

The apparatus may be configured to deploy an object in a bore. In suchan arrangement any sticking or jamming of an object during suchdeployment may be addressed by the apparatus. In such an arrangement theapparatus may be configured in a disabled configuration duringdeployment of the object, with the apparatus reconfigured into a jarringconfiguration when jarring is required.

The apparatus may be configured to be engaged with an object alreadypresent within a bore. That is, the apparatus may be run into a bore,for example on a connected work string, until engagement of an object isachieved, and then used to assist to free said object.

The apparatus may be configured for use in jarring an object positionedbelow the apparatus in a bore. Alternatively, or additionally, theapparatus may be configured for use in jarring an object positionedabove the apparatus. It should be understood, however, that the termssuch as “upper”, “lower”, “above” and “below” are not intended to onlybe limited with reference to a vertical orientation. Instead, such termsshould be assumed in relation to the entry point of a bore, such that aregion nearer to an entry point may be defined as an upper region, and aregion further from an entry point may be defined as a lower region.

The apparatus may be configured to be self-jarring. That is, theapparatus may be configured to provide a jarring force directed atitself.

The apparatus may be configured to permit axial jarring in one axialdirection, such as an upwardly and downwardly direction. The apparatusmay be configured to permit axial jarring in opposing axial directions,such as both upwardly and downwardly.

The magnitude of an axially applied force between the first and secondimpact surfaces may dictate the magnitude of a generated jarring force.The magnitude of the generated jarring force may be readily adjusted andcontrolled by appropriate variation of the applied axial force, forexample by varying the tension and/or compression within an associatedwork string. This may avoid the limitations of prior art arrangements inwhich the jarring force of a jarring tool may be typically set at apredefined value prior to deployment of the tool, and cannot be variedwhile deployed.

The rotatable jarring arrangement may translate a rotational drivemovement to cause axial separation of the first and second impactsurfaces, and subsequent impact of the first and second impact surfacesto generate an impact therebetween.

The rotatable jarring arrangement may be configured to receiverotational drive movement from a rotational drive mechanism.

The rotational drive mechanism may be configured separately from theapparatus.

The apparatus may comprise a rotational drive mechanism.

The rotational drive mechanism may be coupled or otherwise associatedwith the rotatable jarring arrangement and configured to provide arotational drive movement to the rotatable jarring arrangement.

The rotational drive mechanism may comprise a work string. In such anarrangement the rotatable jarring arrangement may be configured toreceive rotational drive movement from an associated work string whichmay be coupled to the apparatus. In such an arrangement the associatedwork string may be defined as a rotatable work string.

The rotational drive mechanism may comprise a driving component, forexample, an electric motor, pneumatic motor, hydraulic motor or thelike.

The rotatable jarring arrangement may be at least partly defined by orwithin one or both of first and second jarring portions. The rotatablejarring arrangement may be interposed between the first and secondjarring portions. At least a portion of the rotatable jarringarrangement may be defined by one or both of the impact surfaces.

The rotating jarring arrangement may be at least partly defined by amechanism interposed between the first and second jarring portions whichmay be formed and arranged to convert relative rotating movement betweenthe first and second jarring portions to relative linear movementbetween the first and second jarring portions. Such a mechanism may beprovided remotely from at least one impact surface. Such a mechanism maybe incorporated within at least one impact surface.

The rotatable jarring arrangement may be configured to effect relativeaxial translation of the first and second impact surfaces according toengagement of said surfaces and a rotational drive movement.

The first and second impact surfaces may define respective unevensurface profiles. The uneven surface profiles may be defined by surfacevariations in the associated impact surfaces. The first and secondimpact surfaces may be configured to be engaged and rotated relative toeach other, for example by relative rotation of associated first andsecond jarring portions, established by a rotational drive mechanismsuch that rotating sliding engagement of the respective uneven surfaceprofiles generates an impact force therebetween.

The respective profiles of the first and second impact surfaces may beconfigured to permit a rotational impact force to be generatedtherebetween upon relative rotating sliding engagement of the surfaces.

The apparatus may be configured to permit an axial force to be appliedbetween the first and second impact surfaces, at least when theapparatus is in a jarring configuration, such that a combination of theaxial force and relative rotation applied between the impact surfacespermits the respective profiles to generate an impact forcetherebetween. The axially applied force may function to press the firstand second impact surfaces together. The axially applied force may beestablished by a connected work string. Such a connected work string mayapply a compressive or tensile axial force to establish an axial forcebetween the first and second impact surfaces.

Respective profiles of the first and second impact surfaces may beconfigured such that during rotating sliding engagement of the impactsurfaces, portions of the surfaces become separated against the actionof an axially applied force, and separated portions subsequentlyimpacted together to generate the impact force. Such separation againstthe action of the axial force may permit energy to become stored to besubsequently released during impact of the surface portions. Inembodiments where an axial force is applied between the first and secondimpact surfaces by a connected work string, energy may become storedwithin the connected work string, for example as tension or compressionwithin said work string.

Respective profiles of the first and second impact surfaces may beconfigured such that separation of the impact surfaces occurs over afirst time period, and subsequent impact following this separationoccurs over a second time period which is shorter than the first timeperiod. Such an arrangement may permit an increase in the impulse forcewhich may be generated.

The profiles of the first and second impact surfaces may be defined byramp structures circumferentially distributed around the impactsurfaces, wherein rotatable interengagement of the ramp structurespermits axial separation and reengagement of the surfaces. The profilesmay be defined by teeth structures, such as serrated teeth, ratchetteeth or the like. The profiles may be defined by respective camsurfaces.

The rotatable jarring arrangement may comprise inter-engaging surfacesprovided separately or remotely from the first and second impactsurfaces, wherein the inter-engaging surfaces cooperate upon relativerotation to provide relative axial movement of the first and secondimpact surfaces to generate an impact force therebetween. In such anarrangement the inter-engaging surfaces may be provided between thefirst and second jarring portions.

The rotatable jarring arrangement may comprise an engaging memberconfigured to engage with a circumferential surface. The engaging membermay be associated with one of the first and second jarring portions, andthe circumferential surface may be associated with the other of thefirst and second portions. A jarring effect may be achieved by relativerotation of the circumferential surface and engaging member.

The circumferential surface may be defined by a circumferential track.The circumferential track may comprise surface variations, for example,undulations, teeth or the like.

The circumferential surface may be configured in combination with anadditional, axially-separated circumferential surface to define a slottherebetween. The slot may be configured to accommodate the engagingmember. The engaging member and the slot may be configured to rotaterelatively such that the engaging member may be engaged with at leastone of the circumferential surfaces upon relative rotation of theengaging member and the slot.

The circumferential track may be rotated by the rotating drive movement.

The engaging member may be rotated or moved along a circumferential pathby a rotating drive movement.

The engaging member may be configured to be continuously engaged withthe circumferential track upon relative rotation of the engaging memberand the circumferential track. The engaging member may comprise, forexample, a pin, rod, plate or the like.

Relative rotational movement of the circumferential track and theengaging member may be achieved by rotating the engaging member relativeto the circumferential track, which may be rotationally fixed within itsassociated jarring portion.

Relative rotational movement of the circumferential track and theengaging member may be achieved by rotating the circumferential trackrelative to the engaging member, which may be rotationally fixed withinits associated jarring portion.

Relative rotational movement of the circumferential track and theengaging member may be achieved by rotating both the engaging member andthe circumferential track,

The engaging member may be configured to continuously engage with thecircumferential track upon relative rotation of the engaging member andthe circumferential track.

Relative rotational movement of the engaging member and thecircumferential track may translate the relative rotational movementinto relative axial movement of the first and second impact surfaces tofacilitate axial impact therebetween.

The engaging member may be configured to extend radially from one of thefirst or second portions to engage with the track associated with theother of the first or second portions. The engaging member may extendoutwardly from a central axis of the first or second portions. Theengaging member may extend inwardly towards the central axis of thefirst or second portions.

The rotatable jarring arrangement may comprise a pressurising apparatussuch as a pump and/or compressor configured to respond to or be drivenby a rotating drive movement to provide fluid communication of anactuating fluid between first and second fluid reservoirs, for use infacilitating impact between the first and second impact surfaces.

The pressurising apparatus may be configured to provide a pressuredifferential between the first and second fluid reservoirs.

The pressurising apparatus may be configured in a pressurising stage,wherein the second fluid reservoir may be pressurised.

The pressurising apparatus may be configured in a de-pressurising stage,wherein the second fluid reservoir may be de-pressurised.

The pressurising apparatus may be configured in a disabled stage,wherein the pressurising apparatus may be prevented from providing fluidcommunication between first and second fluid reservoirs.

The pressurising apparatus may be configured in the pressurising stageto cause relative axial separation of the first and second impactsurface. Upon pressurisation, actuating fluid may be communicated fromthe first fluid reservoir to the second fluid reservoir, thereby forcingthe first and second impact surfaces to separate relatively in an axialdirection.

The pressurising apparatus may be configured in the de-pressurisingstage to de-pressurise the second fluid reservoir. The pressure in thesecond reservoir may be released upon reaching a threshold limit, forexample, a maximal relative separation of the impact surfaces, at apressure limit, or the like. Upon pressure release, actuating fluid maybe communicated from the second reservoir to a first reservoir via apressure release system. A conduit, flow path or the like may beselectively provided for communication of actuating fluid from secondreservoir to the first reservoir. A valve system may be configured tomaintain relative pressurisation of the first and second reservoirs,until the threshold limit may be achieved.

When provided in the de-pressurisation stage the second reservoir mayde-pressurise by communicating actuating fluid from the second reservoirto the first reservoir, thereby permitting the first and second impactsurfaces to move axially together such that an impact force may begenerated therebetween.

The valve system may be configured to prevent fluid communicationbetween the first and second reservoirs, thereby permittingre-pressurisation of the second reservoir according to rotational drivemovement of the pressurising apparatus.

The pressurising apparatus may be configured to cycle between thede-pressurising state and the pressurising state to facilitate cyclicalimpact between the first and second impact surfaces.

The pressurising apparatus may be configured to generate multipleimpacts upon subsequent cycles of pressurisation and de-pressurisation.

The rotatable jarring arrangement may comprise a rotating lobearrangement, wherein the rotating lobe arrangement may be interposedbetween the first and second jarring portions, and wherein the rotatinglobe arrangement may be configured to be rotated by the rotating drivemovement for use in facilitating impact between the first and secondimpact surfaces.

The rotating lobe arrangement may comprise a lobe, for example, a cam,eccentric disc or the like, wherein the lobe may be configured to beengaged with a lobe contact surface, and wherein the lobe may be shapedto generate relative axial movement of the first and second impactsurfaces upon rotation of the lobe relative to the lobe contact surface.

Rotation of the rotating lobe arrangement may facilitate impact betweenthe first and second impact surfaces by rotating movement of the loberelative to the additional surface.

The lobe may be configured to be frictionally engaged with the lobecontact surface, such that when rotated relative to the lobe contactsurface the lobe translates in a direction, for example, acircumferential direction.

The lobe may be configured to be slidably engaged with the lobe contactsurface, such that when rotated relative to the lobe contact surface,the lobe remains in a relative static location, for example, a relativestatic circumferential location.

The rotating lobe arrangement may comprise a plurality of lobes.

The rotatable jarring arrangement may be configured to generate at leastone jar or jar event for a single full 360 degree revolution of anassociated rotating drive movement. Accordingly, multiple revolutions ofthe rotating drive movement may be configured to generate multiple jars.This arrangement may permit multiple jars to be generated withoutrequiring a complete resetting of the apparatus as may be required inknown linear jarring tools.

The apparatus may be configured to generate multiple jars for a single360 degree revolution of the rotating drive movement.

The jarring frequency of the apparatus may be dictated by the relativerotational velocity of an associated rotating drive movement, and thenumber of jars generated by the rotating drive movement for a singlerelative rotation.

The provision of a jarring force by use of the rotating drive movementmay permit a higher jarring frequency to be achieved. The ability toachieve such higher frequencies may permit an object engaged with theapparatus to be effectively vibrated, rather than only receive theeffect of a single or infrequent jarring force. This ability toeffectively vibrate an object may provide significant advantages. Forexample, a higher jarring frequency or application of a vibratory forceto any solid particulate which is in contact with an object, for exampledue to collapse of the bore, may result in a condition termed ‘SolidParticulate Liquefaction’. This phenomenon essentially converts thebehaviour of the solid particles within the region of the object to thatof a liquid, reducing the shear strength of the solid and allowing theobject to be more readily freed from any bind with the solid particles.

Furthermore, the ability to apply higher frequency jarring, andoptionally in combination with the ability to provide increased controlover the magnitude of the jarring force, may improve the ability toaddress any stick-slip bind between an object and a bore wall orcollapsed bore wall. Conventional jars which deliver high amplitude/lowfrequency jarring are typically unproductive in this environment(particularly as the jar re-setting action often counters any gainmade).

The jarring frequency of the apparatus may be controlled by controllingthe rotational velocity of an associated rotating drive movement. Suchan arrangement may provide improved control of the jarring frequency,for example by permitting the jarring frequency to be infinitely varied.This improved control may provide a significant improvement over knownjarring tools in which the jarring frequency is typically dictated orlimited by the time required to reset the tool.

The ability to readily control the jarring frequency, for example in aninfinitely variable manner, by controlling the rotational velocity of anassociated rotating drive movement may permit a user to adjust thejarring frequency in accordance with specific requirements.

The apparatus may be configured to provide a jarring frequency of, forexample, between 0 Hz and 20 kHz, for example between 0.5 Hz and 5 kHz,for example between 0.5 Hz and 1 kHz, such as between 0.5 Hz and 100 Hz,for example between 0.5 Hz and 20 Hz.

In one embodiment the ability to readily vary the jarring frequency maypermit an object engaged with the apparatus to be vibrated at itsresonant or natural frequency (or a selected preferred harmonicfrequency). This may allow the delivery of impact loading to far higherlevels than would be achievable using conventional jars, yet withsignificantly reduced input forces. Further, when vibrating at resonantor a harmonic frequency, an elongate object, such as a tubing string,tool string or the like, may be caused to oscillate (wobble) in asinusoidal wave pattern within the bore. This may assist greatly withreducing the level of contact between the object and the sticking mediumand will significantly contribute to breaking any differential pressuretype sticking (differential sticking).

The ability to vary jarring frequency may permit the apparatus to beused to provide a single jarring event.

The apparatus may comprise a plurality of rotatable jarringarrangements.

The apparatus may comprise different types of rotatable jarringarrangements to provide different jarring forces.

The apparatus may be configured to provide different jarring forces withdifferent characteristics, for example, in terms of force amplitude,frequency or relative phase of said jarring forces.

The apparatus may be configured such that each of the rotatable jarringarrangements may be separately selected to provide a jarring force witha different characteristic.

The apparatus may be configured to provide sequential jarring forces bysequentially selecting the different rotatable jarring arrangements.

The apparatus may be configured to provide jarring forces such that theamplitude, frequency or phase of the jarring forces may be varied topreferentially provide jarring forces, for example, a higher frequency,lower amplitude jarring force to disturb the stuck object in combinationwith a lower frequency, higher amplitude jarring force to furtherdisturb the stuck object.

In some embodiments the apparatus may be provided in combination with amonitoring system configured to monitor properties associated with ajarring action, for example to permit any resonant behaviour to bemonitored and allow adjustment of the jarring frequency and/or magnitudeaccordingly. Such a monitoring system may comprise one or more sensors,such as accelerometers, vibration sensors, acoustic sensors or the like.

The apparatus may be configurable from a disabled configuration in whichthe impact surfaces are prevented from being axially impacted together,and a jarring configuration in which the impact surfaces are permittedto be axially impacted together and generate an impact forcetherebetween. As the jarring effect of the apparatus may thus only beachieved when in the jarring configuration, the apparatus may beselectively activated to provide jarring. That is, when the apparatus isconfigured in the disabled configuration the jarring effect may bedeactivated. Accordingly, the apparatus may provide extendedfunctionality when in its disabled configuration, such as being able todeploy and/or actuate or operate other components or objects, whereinsuch functionality may be difficult or impossible when the apparatus isconfigured in its jarring configuration.

When the apparatus is in the disabled configuration the rotatablecoupling between the first and second jarring portions may permit torqueto be transferred therebetween. Accordingly, in this disabledconfiguration the first and second portions may be rotated together, forexample by a connected work string. Such ability to transmit torquebetween the first and second portions may permit the apparatus to beused to rotate an object engaged with the apparatus.

The first jarring portion may be configured to be rigidly coupled to awork string. The first jarring portion may be configured to be directlycoupled to a work string. The first jarring portion may be configured tobe indirectly coupled to a work string, for example by use of anintermediate component or structure interposed between the first jarringportion and work string. The first jarring portion may comprise aconnector configured to permit connection with a work string. Theconnector may comprise a threaded connector or the like.

The second jarring portion may be configured to engage an object byabutting said object. The second jarring portion may be configured to becoupled to an object. The second jarring portion may be configured to berigidly coupled to an object. The second jarring portion may beconfigured to be directly coupled to an object. The second jarringportion may be configured to be indirectly coupled to an object, forexample by use of an intermediate component or structure interposedbetween the second jarring portion and object. In such an arrangement ajarring force generated within the apparatus may be transmitted to theobject via the intermediate component. The second jarring portion maycomprise a connector configured to permit connection with an object. Theconnector may comprise a threaded connector or the like.

When the apparatus is connected to a work string, said apparatus may beconsidered to form part of the work string.

When the apparatus is engaged or connected with an object, the apparatusand engaged or connected object may become part of the work string.

The work string may comprise any structure capable of being secured tothe apparatus and for being deployed through a bore. The work string maycomprise any structure capable of being rotated to impart torque to orwithin the apparatus, for example to the first jarring portion. The workstring may comprise an elongate structure. The work string may comprisea pipe or pipe structure, such as multiple pipes or tubulars coupledtogether, coiled tubing or the like.

The work string may comprise a drill string or a portion of a drillstring. In such an arrangement the apparatus may be configured as adrilling jarring apparatus. The work string may comprise one or more ofdrill pipe, drill collars, stabilisers and the like.

The work string may comprise a prop shaft coupled to a motor, such as asurface motor, downhole motor or the like, wherein said prop shaft mayfunction to transmit torque from such a motor to or within theapparatus, such as to the first jarring portion.

The object may comprise any object which is or may be located within abore. The object may comprise multiple components secured together. Theobject may comprise a downhole tool. The object may comprise a furtherwork string. The further work string may comprise a portion of a drillstring.

The object may comprise a drilling assembly, such as a bottom holedrilling assembly. The object may comprise a drill bit for use indrilling the associated bore. In such an arrangement when the apparatusis configured in a disabled configuration, torque applied to the firstjarring portion via a connected work string may be transmitted to thesecond jarring portion and subsequently to an associated drill bitsecured or engaged with the second jarring portion. Accordingly, thedrill bit may be rotated to drill the bore via torque applied by thework string. In the event of the drill bit or any associated apparatus,such as any associated bottom hole assembly, becoming stuck or jammedwithin the bore, the apparatus may be reconfigured to the jarringconfiguration such that further torque applied by the work string may beused to generate the impact force and apply jarring to the drill bit orassociated apparatus. This may assist to free and/or advance the drillbit and any associated apparatus.

In one embodiment the apparatus may be configured to be secured within adrill string. The apparatus may be configured to be interposed betweendifferent sections of a drill string. The apparatus may be configured toform part of a drill string.

When the apparatus is configured in the jarring configuration one of thefirst and second jarring portions may be rotatably fixed, and the otherof the first and second jarring portions may be rotatable to permitrelative rotation between the impact surfaces. One of the first andsecond jarring portions may be rotatably fixed by engagement with anobject which is also rotatably fixed, for example by being stuck withinthe bore.

When the apparatus is configured in the jarring configuration one of thefirst and second jarring portions may be axially fixed, for example byengagement with an object which is also axially fixed, for example bybeing stuck in a bore. Such an arrangement may permit an axial force tobe applied between the first and second jarring portions via a connectedwork string, for example to establish an axial force between the firstand second impact surfaces.

The apparatus may be reconfigured towards the jarring configuration byapplication of a predetermined force between the first and secondjarring portions. The predetermined force may comprise a rotationalforce. The predetermined force may comprise an axial force. Thepredetermined force may be generated by a connected work string.

The rotating jarring arrangement may provide a finite relative axialmovement of the impact surfaces according to the configuration of therotating jarring arrangement. The finite relative axial movement mayrestrict movement of the impact surfaces and reduce any effective impactforce therebetween. The apparatus may comprise an internal tensioningmechanism to increase any effective impact force. The internaltensioning mechanism may be configured to provide tensioning orde-tensioning capabilities to permit sufficiently rapid impact of theimpact surfaces to generate an impact force therebetween. The internaltensioning mechanism may be configured to provide tensioning orde-tensioning capabilities to prevent rapid impact of the impactsurfaces. Tension provided by an associated work string may operate theinternal tensioning mechanism.

When the apparatus is in the disabled configuration the rotatablejarring arrangement may be configured to prevent relative movement ofthe first and second impact surfaces to prevent an impact between theimpact surfaces. The apparatus may be configured in the disabledconfiguration when the rotational drive movement is prevented fromrotating the rotatable jarring arrangement.

When the apparatus is in the disabled configuration the rotatablejarring arrangement may be configured to permit relative movement of thefirst and second impact surfaces while preventing impact between thefirst and second impact surfaces. The apparatus may be configured in thedisabled configuration when the rotational drive movement permitsrotation of the rotatable jarring arrangement.

When the apparatus is in the disabled configuration the rotatablejarring arrangement may be configured to permit relative movement of thefirst and second impact surfaces and engagement between the first andsecond impact surfaces. In this disabled configuration the engagementbetween the impact surfaces may not generate a sufficient impact forcetherebetween to generate a jarring effect.

In certain embodiments the apparatus may be configured such that initialengagement of the impact surfaces during reconfiguration of theapparatus towards the jarring configuration generates an impact forcebetween said impact surfaces. This may permit an initial jarring forceto be generated during reconfiguration of the apparatus, which is thenproceeded by the rotary jarring effect of the first and second impactsurfaces when subsequently rotated relative to each other, for example.

The first and second impact surfaces may be axially separated when theapparatus is in the disabled configuration. In such an arrangementreconfiguration of the apparatus to the jarring configuration may beachieved by establishing relative axial movement of the first and secondjarring portions to engage the impact surfaces. In one embodiment suchaxial movement may be permitted upon application of a predeterminedaxial force.

The first and second jarring portions may be configured to be axiallytelescoped relative to each other. Such an arrangement may permit thejarring portions to be moved axially relative to each other, for exampleto reconfigure the apparatus from the disabled configuration to theengaged configuration.

The first and second jarring portions may be configured to be axiallycoupled together. Such an axial connection may permit axial load to betransmitted between the first and second jarring portions in at leastone direction. For example, such an axial connection may permit an axialload, such as an axial compression load, to be transmitted to an objectvia the apparatus. In one embodiment such an arrangement may permitweight to be applied to a drill bit engaged with the second jarringportion.

The axial connection between the first and second jarring portions maybe releasable, for example to permit reconfiguration of the apparatus.The axial connection between the first and second jarring portions maybe configured to be released upon application of a predetermined force.

The apparatus may comprise a connection arrangement configured toprovide a releasable connection between the first and second jarringportions, wherein release of the connection arrangement may permit theapparatus to be configured between the disabled and jarringconfigurations.

The releasable connection may be configured to be released upon exposureto a predetermined force.

The connection arrangement may be configured to provide a releasablerotatable connection between the first and second jarring portions. Theconnection arrangement may comprise a spline arrangement. The connectionarrangement may comprise at least one spline or equivalent structuremounted on the first jarring portion, and at least one correspondingspline or equivalent structure mounted on the second jarring portion. Insuch an arrangement the splines may be arranged to be engaged when theapparatus is in the disabled configuration, and disengaged when theapparatus is in the jarring configuration. Such disengagement of thesplines may be achieved by relative axial movement of the first andsecond jarring portions.

The connection arrangement may comprise a radial member which extendsradially between the first and second jarring portions to provide arotatable connection therebetween, wherein said radial member may beconfigured to be disengaged with at least one of the first and secondjarring portions, for example upon application of a predetermined force,such as a predetermined torque.

The connection arrangement may comprise a frangible component extendingbetween the first and second jarring portions and configured to bebroken, for example sheared upon application of a predetermined force.

The connection arrangement may comprise a clutch interposed between thefirst and second jarring portions to provide a rotatable connectiontherebetween. Deactivation of said clutch may be achieved uponapplication of a predetermined torque between the first and secondjarring member. In some embodiments, in a first clutch configuration afull rotatable connection may be achieved between the first and secondjarring portions. In a second clutch configuration relative rotationbetween the first and second jarring portions may be permitted. In thesecond clutch configuration the clutch may be entirely or completelydisengaged such that the clutch does not interfere with relativerotation between the first and second jarring portions. In otherembodiments, in the second clutch configuration the clutch may provide adegree of torque drag. Such torque drag may permit relative rotation ofthe first and second jarring portions during a jarring operation, yetmay provide an instantaneous rotatable connection between the jarringportions, for example at the moment of release of an object beingjarred.

The connection arrangement may be configured to provide a releasableaxial connection between the first and second jarring portions.

The releasable axial connection may comprise a radial member whichextends radially between the first and second jarring portions, whereinsaid radial member may be configured to be disengaged from at least oneof the first and second jarring portions, for example upon applicationof a predetermined force, such as a predetermined axial force. Such aradial member may be defined by a key member. A plurality of radialmembers may be provided.

The connection arrangement may comprise a frangible component extendingbetween the first and second jarring portions and configured to bebroken, for example sheared, upon application of a predetermined force,such as a predetermined axial force.

The connection arrangement may be configured to provide a rigid axialconnection such that relative axial movement of the first and secondjarring portions is prevented until the connection is released.

The connection arrangement may be configured to provide a flexible axialconnection between the first and second jarring portions. Such aflexible connection may permit a degree of relative axial movementbetween the first and second jarring portions prior to release of theaxial connection. The flexible axial connection may be configured torestrict relative axial movement between the first and second jarringportions prior to release of the axial connection. Such a flexibleconnection may permit energy to become stored within the apparatus orassociated components, such as a connected work string and/or engagedobject for use in applying a jarring force between the first and secondimpact members upon release of the axial connection.

The connection arrangement may comprise an elastic arrangement, such asa spring arrangement, configured to be deformed upon initial relativeaxial movement between the first and second jarring portions prior torelease of the axial connection. This elastic arrangement may beconfigured to store energy within the apparatus during initial relativeaxial movement between the first and second jarring portions. Suchenergy may be utilised to permit release of any axial connection, and/orto facilitate an initial impact force between the first and secondimpact surfaces.

The connection arrangement may define a triggering arrangement to permitthe apparatus to be triggered to be configured from the disabledconfiguration to the jarring configuration.

The connection arrangement may be configured to provide both areleasable axial connection and a releasable rotary connection betweenthe first and second jarring portions. In one embodiment release of theaxial connection may permit the first and second jarring portions to bemoved axially relative to each other, with this axial movementpermitting the rotary connection to be released, for example to permitinitially engaging splines of the first and second jarring portions tobecome disengaged, to permit a clutch to be at least partiallydisengaged, to disengage radial members or the like.

The apparatus may comprise a clutch assembly provided between the firstand second jarring portions. The clutch assembly may be configured toestablish a rotatable connection between the first and second jarringportions upon release of a stuck object which is engaged with the secondjarring portion. This arrangement may permit the object to be rotatedimmediately upon release or unsticking which may assist in prevent theobject from become stuck again, for example to assist to ream the bore.The clutch assembly may establish a predetermined drag torque betweenthe first and second jarring portions, wherein relative rotationalmovement of the first and second jarring portions is permitted when thisdrag torque is exceeded.

The apparatus may be reconfigurable from the jarring configuration tothe disabled configuration. Such an arrangement may permit the apparatusto be re-settable.

An aspect of the present invention relates to a method for use injarring an object in a bore.

This method may be performed by use of an apparatus according to anyother aspect. Accordingly, any features and/or described methods,options and functionality of the apparatus of any aspect may be assumedto also relate to this method.

The method may comprise cause relative axial movement and impact betweenfirst and second impact surfaces within a jarring apparatus, whereinsaid axial movement is caused by a rotational drive movement.

The method may comprise:

connecting a first jarring portion of a jarring apparatus to a workstring, wherein the first jarring portion includes a first impactsurface;

engaging a second jarring portion of the jarring apparatus with anobject, wherein the second jarring portion includes a second impactsurface; and

applying a rotational drive movement to a rotatable jarring arrangementassociated with at least one of the first and second jarring portions tocause relative axial movement of the first and second impact surfaces toestablish axial impact therebetween and thereby applying a jarring forceto the object;

The method may comprise reconfiguring the apparatus from a disabledconfiguration in which the first and second impact surfaces areprevented from being axially impacted together to a jarringconfiguration in which the first and second impact surfaces arepermitted to be axially impacted together to generate an impact forcetherebetween.

When in the disabled configuration the impact surfaces may be axiallyseparated, wherein the method comprises moving the impact surfacesaxially relative to each other to establish engagement of the first andsecond impact surfaces. The method may comprise moving the first andsecond impact surfaces axially relative to each other to generate animpact force therebetween.

An aspect of the present invention relates to an apparatus for use injarring an object in a bore, comprising:

a first jarring portion including a first circumferential impact surfacedefining an uneven surface profile; and

a second jarring portion including a second circumferential impactsurface also defining an uneven surface profile,

wherein the first and second impact surfaces are configured to berotated relative to each other such that rotating sliding engagement ofthe respective uneven surface profiles generates at least one impactforce therebetween.

The first and second impact surfaces may be configured to be axiallymoved relative to each other to engage the first and second impactsurfaces and generate a first impact force therebetween, and to besubsequently rotated relative to each other such that rotating slidingengagement of the respective uneven surface profiles generates at leasta second impact force therebetween.

An aspect of the present invention relates to a downhole jarringapparatus for use in jarring an object in a bore, comprising:

a first profiled impact surface; and

a second profiled impact surface,

wherein the first and second impact surfaces are configured to berotated relative to each other to cause circumferential slidingengagement of the profiled surfaces to establish an impact force betweenthe first and second portions.

An aspect of the present invention relates to a jarring apparatus foruse in jarring an object in a bore, comprising:

a first jarring portion comprising a first impact surface which definesa first circumferential profile; and

a second jarring portion comprising a second impact surface whichdefines a second circumferential profile,

wherein the apparatus is configurable between a first configuration inwhich the first and second impact surfaces are axially separated and thefirst and second portions are rotatably coupled together, and a secondconfiguration in which the first and second impact surfaces are axiallymoved together to be engaged and the first and second portions arerotatably decoupled to permit relative rotational movement therebetweento cause the circumferential profiles of the engaged first and secondimpact surfaces to create an impact force therebetween.

An aspect of the present invention relates to a jarring apparatus foruse in jarring an object in a bore, comprising:

a first impact surface; and

a second impact surface,

wherein a rotating drive movement is configured to rotate a rotatablejarring arrangement to sequentially axially separate and axially engagefirst and second impact surfaces, whereby engagement of the first andsecond impact surfaces generates an impact force therebetween.

Subsequent rotation of the rotating drive movement may generatesubsequent impact forces.

An aspect of the present invention relates to a jarring apparatus foruse in jarring an object in a bore, comprising:

an engaging member; and

a circumferential surface,

wherein the engaging member is configured to be engaged with thecircumferential surface, and wherein the engaging member andcircumferential surface is rotated circumferentially relative to eachother by a rotating drive movement to sequentially axially separate andaxially engage first and second impact surfaces, whereby engagement ofthe first and second impact surfaces generates an impact forcetherebetween.

Subsequent rotation of the rotating drive movement may generatesubsequent impact forces.

An aspect of the present invention relates to a jarring apparatus foruse in jarring an object in a bore, comprising:

a first impact surface;

a second impact surface; and

a pressurising apparatus configured to pressurise and/or de-pressurise acavity,

wherein the apparatus is re-configurable between a first configurationin which the first and second impact surfaces are prevented fromimpacting each other, and a second configuration in which the first andsecond impact surfaces are subsequently impacted together throughde-pressurisation of the cavity, and a third configuration in which thefirst and second impact surfaces are subsequently axially separatedthrough pressurisation of the cavity.

The apparatus may be configured to cyclically pressurise andde-pressurise the cavity to permit subsequent impacts between the firstand second impact surfaces, thereby providing a jarring effect.

An aspect of the present invention relates to a jarring apparatus foruse in jarring an object in a bore, comprising:

a first jarring portion comprising a first impact surface; and

a second jarring portion comprising a second impact surface;

wherein a rotating lobe arrangement is configured to engage with a lobecontact surface, whereupon rotation of the rotating lobe arrangement bya rotating drive movement causes relative axial movement of the firstand second impact surfaces to generate an impact force therebetween.

Subsequent rotation of the rotating drive movement may generatesubsequent impact events thereafter.

It should be understood that one or more features defined in relation toone aspect may be provided in combination with any other aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic illustration of a jarring apparatus accordingto an embodiment of the present invention, wherein the apparatus isshown in partial cut-away and configured in a disabled configuration;

FIG. 2 is a diagrammatic illustration of the jarring apparatus of FIG.1, shown in a jarring configuration;

FIGS. 3a and 3b illustrate a sequential operation of a jarring apparatusaccording to a further embodiment of the present invention;

FIGS. 4a to 4c illustrate a sequential operation of a jarring apparatusaccording to a further embodiment of the present invention;

FIGS. 5a and 5b illustrate a sequential operation of a jarring apparatusaccording to a further embodiment of the present invention;

FIG. 6a is an axial view of a rotatable jarring arrangement of thejarring apparatus in FIGS. 5a and 5b ; and

FIG. 6b is a sequence of side views of a rotating lobe arrangement ofthe jarring apparatus in FIGS. 5a and 5b during a rotation cycle.

DETAILED DESCRIPTION OF THE DRAWINGS

A jarring apparatus, generally identified by reference numeral 10, isillustrated in FIG. 1, with a section partially cut-away to revealinternal features. The apparatus 10 is presented in a disabledconfiguration in FIG. 1. The apparatus 10 may be reconfigured to ajarring configuration, as illustrated in FIG. 2.

The apparatus 10 may be utilised to provide a jarring force to anyobject located within a bore, for example to permit freeing of theobject, to permit actuation of the object or the like. However, for thepurposes of the present description the apparatus is for the exemplaryuse of providing a jarring force to a bottom hole drilling assembly 14,which is provided in the form of a lower drilling string which carriesdrilling equipment, including a drill bit (not shown).

The apparatus 10 comprises a lower connector 16 which facilitates arigid connection with the drilling assembly 14. Further, the apparatus10 comprises an upper connector 18 which permits a rigid connection witha drill string 20 for use in deploying the apparatus 10 and connecteddrilling assembly 14 into a bore, and for applying torque and weight tothe drilling assembly 14 to permit the bore to be drilled and advanced.The drill string 20 will typically include a combination of drill pipeand drill collars.

The apparatus 10 includes a first or upper jarring portion 22 which isconnected with the drill string 20 via connector 18, and a second orlower jarring portion 24 which is connected with the bottom holedrilling assembly 14 via connector 16. As will be described in moredetail below, the upper and lower jarring portions 22, 24 areconfigurable between a disabled configuration (FIG. 1) in which weightand torque may be transmitted between the drill string 20 and drillingassembly 14 to advance the bore, and a jarring configuration (FIG. 2) inwhich a jarring force may be generated therebetween to be applied to thedrilling assembly 14, for example to assist in freeing this assembly inthe event of becoming stuck within the bore.

The upper jarring portion 22 includes a mandrel 26 which is receivedwithin a sleeve portion 28 of the lower jarring portion 24, wherein thismandrel 26 includes an impact member 30 which includes a circumferentialimpact surface 32 defined by a number of circumferentially arrangedteeth 34. The sleeve 28 of the lower jarring portion 24 includes acorresponding impact member 36 which also includes a circumferentialimpact surface 38 defined by a number of circumferentially arrangedteeth 40. The impact member 30 and corresponding impact member 36 makeup a rotatable jarring arrangement 37, wherein the rotatable jarringarrangement 37 provides a jarring force, as required.

The apparatus 10 comprises a releasable axial connection arrangement 41which functions to provide a releasable axial connection between thejarring portions 22, 24. This axial connection arrangement 41 permitsthe jarring portions 22, 24 to be axially secured together when theapparatus 10 is in the disabled configuration of FIG. 1, and be axiallydecoupled to permit reconfiguration towards the jarring configuration,as in FIG. 2. As will be described in further detail below, in thepresent embodiment this axial connection arrangement 41 also functionsas a triggering mechanism to permit the apparatus 10 to be reconfiguredtowards the jarring configuration.

The axial connection arrangement 41 is provided by a shoulder 42 on alower end of the mandrel 26, a release ring 44, and a spring member 46which extends between the shoulder 42 and a release ring 44. When in thedisabled configuration, as shown in FIG. 1, the release ring 44 isrigidly secured to the sleeve 28 of the lower jarring portion 24 via anumber of releasable keys 48. The connection arrangement 41 permits thejarring portions 22, 24 to be axially secured together in the disabledconfiguration such that the impact members 30, 36 are axially separatedand the respective impact surfaces 32, 38 are disengaged. As will bedescribed in further detail below, the axial connection arrangement 41may be released upon application of a predetermined axial force, appliedvia the drill string 20, which causes the keys 48 to release anddecouple the release ring 44 from the sleeve 28.

The apparatus 10 further comprises a releasable rotary connectionarrangement 50 which permits the jarring portions 22, 24 to be rotatablyconnected together when the apparatus 10 is in the disabledconfiguration of FIG. 1, and rotatably decoupled when the apparatus isin its jarring configuration of FIG. 2. This rotary connectionarrangement 50 permits the transmission of torque between the jarringportions 22, 24 when the apparatus 10 is in the disabled configuration.

The rotary connection arrangement 50 comprises a plurality ofcircumferentially distributed and axially extending spline members 52provided on the upper jarring portion 22, and a plurality ofcorresponding spline members 54 provided on the lower jarring portion.When the respective spline members 52, 54 are intermeshed, as in FIG. 1,a rotatable coupling between the jarring portions 22, 24 is achieved.This rotatable coupling may be released by axially separating thejarring portions 22, 24 to disengage the splines 52, 54, as shown inFIG. 2. Such axial separation may be permitted following release of theaxial connection arrangement 41, as described in more detail below.

However, in some embodiments the separate rotary connection arrangement50 may not be essential, and the rotary connection may be achieved bythe axial connection arrangement 41. For example, the keys 48, whenextended, may permit torque to be transferred between the jarringportions 22, 24. As such, the separate spline arrangement 52, 54 may beomitted.

The operation of the apparatus 10 will now be described, with referenceto both FIGS. 1 and 2.

The apparatus 10 is initially configured in the disabled configuration,as show in FIG. 1, and secured to both the drilling assembly 14 and thedrill string 20. A bore may then be drilled, with weight and torquebeing transmitted through the apparatus 10 to the drilling assembly 14.

If the drilling assembly 14 should become stuck within the bore, forexample due to collapse of the bore, the apparatus 10 may then bereconfigured to the jarring configuration, as in FIG. 2. In thisrespect, tension may be established within the drill string 20, forexample by pulling upwardly from surface, to thus apply an axial forcebetween the first and second jarring portions 22, 24, with the secondjarring portion 24 providing a reaction to this axial force by beingrigidly secured to the stuck lower drilling apparatus 14.

The applied axial force will initially cause the spring member 46 tobecome compressed between the shoulder 42 and the release ring,permitting energy to become stored within the entire system. Once theaxial force reaches a predetermined magnitude, the keys 48 of therelease ring 44 will be deactivated, thus releasing the connectionbetween the jarring portions 22, 24, with the stored energy beingreleased and the upward axial force applied by the drill string 20causing the upper jarring portion 22 to move upwardly relative to thelower jarring portion 24 at a relatively high velocity until thesurfaces 32, 38 of the respective impact members 30, 36 impact eachother, generating an impact force therebetween. This initial impactforce may function to jar the stuck drilling assembly 14, and contributetowards freeing this. This upward movement of the upper jarring portion22 also disengages the splines 52, 54 of the rotary connectionarrangement 50, permitting the jarring portions 22, 24 to becomerotatably decoupled. However, as noted above, the keys 48 mayalternatively provide a rotary coupling, such that release of the keys48 also releases the rotary coupling.

Once the apparatus 10 is configured in this jarring configuration, andif the initial jarring force generated by initial impact of the impactmembers 30, 36 did not free the drilling assembly 14, tension is appliedto the drill string 20 to pull on the upper jarring portion 22 and pressthe impact surfaces 32, 38 together, and the drill string 20 alsorotated to rotate the upper jarring portion 22 relative to the lowerdrilling portion 24. This relative rotation establishes rotating slidingengagement of the surfaces 32, 38, such that interaction of the teeth34, 40 causes the surfaces 32, 38 to continuously be separated andreengaged, thus establishing a repeated impact force therebetween, whichwill providing jarring to the stuck drilling assembly 14 through thelower jarring portion 24. This jarring may effectively assist to freethe drilling assembly 14.

The apparatus 10 further comprises a clutch arrangement 55 whichincludes a clutch member 56 in engagement with the sleeve 28 of thelower jarring portion 24 to establish a drag torque therebetween. Whenthe lower jarring portion 24 is fixed within the bore due to engagementwith a stuck drilling assembly 14, the drill string 20 will be will berequired to establish a torque which exceeds the drag torque of theclutch arrangement 55 to establish rotation of the upper jarring portion22. If at any time during relative rotation and jarring between theupper and lower jarring portions 22, 24 the lower jarring assembly 24should become free, for example due to release of the drilling assembly14, the drag torque established by the clutch arrangement 55 will permitthe upper and lower jarring portions 22, 24 to be rotatably coupled.This may therefore permit the drill string 20 to rotate the lowerjarring portion 24 and connected drilling assembly 14, which may assistin further freeing of the drilling assembly 14, for example bypermitting cleaning or reaming of the bore during this establishedrotation.

In some embodiments, the clutch arrangement 55, or a separate clutcharrangement (not shown), may provide a releasable rotary connectionbetween the jarring portions.

The magnitude of the jarring force achieved may be readily adjusted byadjusting the axial force applied by the drill string 20. Further, thefrequency of jarring may be readily adjusted by adjusting the rotationalvelocity of the drill string 20. Such a level of control of the jarringforce and jarring frequency is not possible with prior art jarringmethods.

This particular jarring arrangement provided by the apparatus 10provides a number of advantages. For example, the ability to generate ajarring force in an axial direction by interaction of the teeth 34, 40,in combination with the application of a near constant uni-axial loadingon the stuck portion by the drill string 20, improves the effect of theapparatus 10 to free the drilling apparatus 14.

Also, the ability to generate a repeated jarring force will permithigher jarring frequencies to be achieved in relation to prior artmethods. The ability to generate a higher jarring frequency may permitthe apparatus 10 to impart vibration to associated equipment, such asthe drilling assembly 14. In this respect, a higher jarring frequency orapplication of a vibratory force to any solid particulate which is incontact with the apparatus 10, drill string 20 or drilling assembly 14,for example due to collapse of the surrounding bore, may result in acondition termed ‘Solid Particulate Liquefaction’. This phenomenonessentially converts the behaviour of the solid particles to that of aliquid, reducing the shear strength of the solid and allowing theapparatus or associated object or equipment to be more readily freedfrom any bind with the solid particles.

Furthermore, the ability to apply higher frequency jarring may improvethe ability to address any stick-slip bind between an object and a borewall or collapsed bore wall.

Also, the ability to readily vary the jarring frequency by controllingthe rotational velocity of the drill string 20 may permit the drillingassembly 14, for example, to be vibrated at its resonant or naturalfrequency (or a selected preferred harmonic frequency). This may allowthe delivery of impact loading to far higher levels than would beachievable using conventional jars, yet with significantly reduced inputforces. Further, when vibrating at resonant or a harmonic frequency, thedrilling assembly 14, which may be elongate in nature, may be caused tooscillate (wobble) in a sinusoidal wave pattern within the bore whichmay assist in addressing certain sticking phenomenon within the ore,such as differential sticking.

In some embodiments the apparatus 10 may be provided in combination witha live active monitoring system 60 to permit any resonant behaviour tobe monitored and allow adjustment of the jarring frequency and/ormagnitude accordingly.

In the present embodiment the apparatus 10 may be resettable such thatdrilling may be continued following a successful jarring operation. Forexample, when the drilling assembly 14 has become free, this may beengaged with the bottom of the bore and weight applied via the drillstring 20 to thus move the upper jarring portion 22 downwardly relativeto the lower portion 24 until the keys 48 of the release ring 44reengage with the sleeve 28 to re-establish the axial connection, anduntil the splines 52, 54 interengage, thus re-establishing the rotaryconnection. As noted above, in some embodiments the releasableconnection may alternatively or additionally be achieve by the keys 48and/or a clutch.

The ability to reset the apparatus may not only permit drilling tocontinue, but may also facilitate multiple initial jars to be achieved.

In the embodiment described above, the impact surfaces 32 and 38 formpart of the rotatable jarring arrangement 37 in that the slidinginteraction of the impact surfaces results in generation of jarringforce. However, the impact surfaces could be configured separately orremotely from the rotatable jarring arrangement such that the impactsurfaces generate the jarring force by responding to axial translationprovided by a separate or remote jarring arrangement. In such amodification, the impact surfaces could be planar.

FIGS. 3a and 3b illustrate a part-sectional diagrammatic view of analternative embodiment of a jarring apparatus 110 which is provided witha rotatable jarring arrangement 137 which comprises a mechanism foreffecting axial movement which is different to the aforementionedrotatable jarring arrangement 37 of FIGS. 1 and 2. The rotatable jarringarrangement 137 is interposed between first and second jarring portionsof the apparatus 110.

The apparatus comprises first and second impact surfaces 158, 160 andthe rotatable jarring arrangement 137 is positioned remotely from theimpact surfaces. A slot 162 is defined by a region between a firstsurface profile 164 and a second surface profile 168. The surfaces 162,166 shown in FIG. 3a accommodate a engaging member 170 therebetween,wherein impact members 130, 136 are shown configured to be separatedaxially, as depicted by arrow 171. The engaging member 170 is connectedto rotating axle 172 which effects rotating drive movement upon engagingmember 170. Rotation of engaging member 170 within the slot 162 resultsin relative axial movement of the impact members 130, 136, wherein theimpact surfaces 158, 160 are impacted together in a direction indicatedby arrow 173 to generate an impact force therebetween, as shown in FIG.3b . Further rotation of engaging member 170 results in separation ofimpact surfaces 158, 160, and if necessary further subsequent impact ofimpact surfaces 158, 160 upon further relative rotation of engagingmember 170 and the additional surfaces 162, 166.

During use, impact members 130, 136 impact together according tomovement of the engaging member within the slot 162. In the presentlyenvisaged embodiment the engaging member 170 is in contact with bothadditional surfaces 162 and 166. However, only one additional surfaceneeds to be in engagement with the engaging member 170, for example, inthis embodiment only the additional surface 166 may be engaged withuneven surface profile 168 as impact member 130 would be pushed againstadditional surface 166 when held under tension provided by a drillingassembly (not shown in the present embodiment) and drill string (notshown in the present embodiment). In other embodiments the converse mayprovide the appropriate engagement between either of additional surfaces162 or 166 and engaging member 170. In an alternative embodiment (notshown) the apparatus may include co-operating annular members in placeof the engaging member 162.

FIGS. 4a to 4c illustrate part-sectional diagrammatic views of analternative embodiment of a jarring apparatus 210 which is provided witha pressurising mechanism for effecting axial movement of the first andsecond impact surfaces. FIGS. 4a to 4c show different stages ofoperation during use of the jarring apparatus described in the secondadditional embodiment.

The apparatus 210 comprises a housing 273 comprising first and secondimpact members 230, 236. The first impact member 230 separates first andsecond fluid reservoirs 274, 276. The second impact member 236 axiallyencloses the second fluid reservoir 276 with first and second impactsurfaces 258, 260 disposed therebetween. A pump 278, for example, aprogressive cavity pump, is disposed between the first and second fluidreservoirs and configured to communicate actuating fluid from the firstfluid reservoir 274 to the second fluid reservoir 276 upon relativerotation of the pump 278 and the first impact member 236. The relativerotation of the pump 278 and first impact member 236 is achieved byrotation of a rotating drive movement, thereby transferring actuatingfluid from the first fluid reservoir 274 to the second fluid reservoir276 in a direction generally indicated by arrows 279. A channel 280 isprovided between first and second fluid reservoirs 274, 276 to providecommunication of actuating fluid therebetween. Actuating fluid iscommunicated from the second fluid reservoir 276 to the first fluidreservoir 274 through channel 280 in a direction indicated by arrow 282in FIG. 4b . Communication of fluid using channel 280 is selectivelyprovided using valve 284.

The communication of actuating fluid from the first fluid reservoir tothe second fluid reservoir results in an increase in fluid pressure inthe second fluid reservoir which results in the axial separation of thesecond impact surface 260 relative to the first impact surface 258 in adirection indicated by arrow 286 in FIG. 4 a.

A valve 284 prevents communication of actuating fluid via channel 280. Alimit trigger 288 is provided to define a threshold beyond whichde-pressurisation of the second fluid reservoir occurs due the valve 284permitting actuating fluid communication from the second fluid reservoir276 to the first fluid reservoir 274 via channel 280. The limit trigger288 may be activated upon reached a mechanical limit in terms ofrelative separation of the impact members, a pressure limit or the like.In the embodiment shown the valve 284 is activated or de-activatedthrough a trigger system comprising a trigger member 292, trigger spring294 which are connected via trigger connector 296 to rotate the valve284 to permit or prevent actuating fluid communication through channel280. Alternative valve or channel arrangements may be envisaged whosepressurisation and de-pressurisation functions are equivalent to theembodiment described herein.

FIGS. 4a to 4c illustrate a sequence of events within a cycle ofpressurisation and de-pressurisation of the apparatus. FIG. 4aillustrates pressurisation of the second fluid reservoir, therebyaxially separating the first and second impact members. FIG. 4billustrates the impact members at their maximum axial separation, asdefined by the trigger limit 288, upon reaching which the valve 284permits communication of actuating fluid from the second fluid reservoir276 to the first fluid reservoir 274 via channel 280. Valve 284 may beconfigured to permit communication of actuating fluid for a pre-definedunit of time. Tension provided between the first and second jarringportions results in rapid de-pressurisation of the second fluidreservoir 276 to permit axial engagement of the first and second impactsurfaces, and hence impact therebetween. Subsequent to the impact of theimpact surfaces, the valve 284 closes to permit subsequentre-pressurisation of the second fluid reservoir 276.

FIGS. 4a to 4c are representative of a cycle of pressurisation andde-pressurisation events to generate a jarring effect. Multiple jarevents could be generated by cyclically operating the apparatus.Alternative configurations of the apparatus described herein could beconceived to equivalently generate the jarring effect.

FIGS. 5a to 5b illustrate part-sectional diagrammatic views of analternative embodiment of a jarring apparatus 310 which is provided by arotating jarring arrangement 337 which comprises a rotating lobearrangement for effecting relative axial movement of the first andsecond impact surfaces. FIG. 6a shows an axial view of the rotatingjarring arrangement 337 and FIG. 6b (i)-(iv) show representative sideviews of the rotating jarring arrangement during a rotational cycle ofthe apparatus.

In reference to FIGS. 5a and 5b the apparatus 310 comprises a firstimpact member 330, which is associated with one of the first or secondjarring portions, and second impact member 336, which is associated withthe other of the first or second jarring portions. First impact member330 comprises a first impact surface 358. Second impact member 336comprises a second impact surface 360. The rotating jarring arrangement337 is rotated by a rotating drive movement directed through axle 372,which effects rotation of rotating lobe arrangement 398. Rotating lobearrangement 398 comprises at least one lobe 3100, which rotates about aradially extending axis 3102. In the depicted embodiment there areprovided a plurality, namely two, of lobe 3100, as shown in FIG. 5b .Rotating lobe arrangement 398 is housed in an accommodating region 3104,which is axially remote from the impact members 330 and 336. Theaccommodating region 3104 comprises upper contact surface 3106 and lowercontact surface 3107. In the present embodiment, the upper contactsurface 3106 of the accommodating region 3104 is maintained inengagement with a circumferential position on lobe contact surface, forexample, shown by 3108 in FIG. 5a and 3110 in FIG. 5b . Rotating drivemovement of the rotating lobe arrangement 398 translates the lobe 3100in a circumferential path while in engagement with upper contact surface3106. During translation in the circumferential path, frictional forceapplied between lobe 3100 and upper contact surface 3106 results insubsequent rotation of the lobe 3100 about the radially extending axis3102. The lobe 3100 are configured to effect relative axial movement ofthe first and second impact surfaces 358 and 360 via axle 372 uponrotation of the lobes 3100 relative to upper contact surface 3106.

In reference to FIGS. 6a and 6b (i)-(iv) to support FIGS. 5a and 5b ,different partial views of the apparatus 310 are shown. The first impactsurface 358 is shown in its maximum axial separation from second impactsurface 360 in FIG. 5a , as indicated by direction arrow 3112. Uponsubsequent rotation of the rotating lobe arrangement 398, the impactsurfaces are shown at or during impact in FIG. 5b , as depicted bydirection arrow 3114. Axial rotation 3116 of the rotating lobearrangement 398 is depicted in FIG. 6a . A cycle of lobe rotation isshown in FIG. 6b (i)-(iv) in which the lobe 3100 is shown during a cycleof rotation. Tension applied via the first and second jarring portionsstores energy within the apparatus such that when the lobe in shown toprovide maximum impact surface separation, as indicated in FIG. 6b (iii)and indicated by arrow 3118, subsequent rotation of the lobe, as in FIG.6b (iv) the rotation of lobe 3100 causes relative rapid axial movementof the impact in a direction depicted by arrow 3120 in FIG. 6b (iv).

It should be understood that tension applied to the apparatus via thework string plays an important part in defining the amplitude of impactbetween first and second impact surfaces in that the resulting storedenergy increases impact force therebetween. In an alternative embodimentthe lobe 3100 may be configured to be in contact with lower contactsurface 3107. In an alternative embodiment the coefficient of frictionbetween the lobe 3100 and lobe contact surface may be adjusted to permitsliding engagement therebetween such that the rotating lobe arrangement398 remains rotationally static with rotation of the lobes about theradially extending axis being actuated by a differential mechanism,which is rotated by a rotating drive movement derived from the centralaxis of the jarring apparatus, thereby maintaining its definition as arotary jarring apparatus.

It should be understood that the embodiments described herein are merelyexemplary and that various modifications may be made thereto withoutdeparting from the scope of the invention. For example, any suitablemechanism may be utilised which can translate a rotational drivemovement to an axial impact movement of impact surfaces. As such, axialimpact may be controlled and initiated by a rotary action or drive.Further, the jarring apparatus is not exclusively for use in drillingapplications, and may be used in any application in which an objectrequires jarring in a bore.

1. A downhole jarring apparatus for use in jarring an object in a bore,comprising: a first jarring portion including a first impact surface; asecond jarring portion including a second impact surface; and apressurising apparatus operable by a rotational drive movement to causerelative axial movement of the first and second impact surfaces toestablish axial impact therebetween.
 2. The downhole jarring apparatusaccording to claim 1, wherein the pressurising apparatus provides fluidcommunication of an actuating fluid between first and second fluidreservoirs, for use in facilitating impact between the first and secondimpact surfaces.
 3. The downhole jarring apparatus according to claim 2,wherein the pressurising apparatus is configured to vary pressurebetween the first and second jarring portions to facilitate relativeaxial movement between the first and second impact surfaces.
 4. Thedownhole jarring apparatus according to claim 2, wherein thepressurising apparatus is configurable between: a pressurising stage,wherein the second fluid reservoir is pressurised; and depressurisingstage, wherein the second fluid reservoir is depressurised.
 5. Thedownhole jarring apparatus according to claim 4, wherein thepressurising apparatus is configurable in the pressurising stage tocause relative axial separation of the first and second impact surfacesby communicating actuating fluid from the first fluid reservoir to thesecond fluid reservoir to pressurise the second fluid reservoir, therebyforcing the first and second impact surfaces to separate relatively inan axial direction.
 6. The downhole jarring apparatus according to claim4, wherein the pressurising apparatus is configurable in thedepressurising stage to depressurise the second fluid reservoir bycommunicating actuating fluid from the second reservoir to the firstreservoir via a pressure release system, thereby permitting the firstand second impact surfaces to move axially together such that an impactforce is generated therebetween.
 7. The downhole jarring apparatusaccording to claim 2, wherein the pressurising apparatus comprises avalve system.
 8. The downhole jarring apparatus according to claim 7,wherein the valve system is configured to prevent fluid communicationbetween the first and second reservoirs, thereby permittingre-pressurisation of the second reservoir according to rotational drivemovement of the pressurising apparatus.
 9. The downhole jarringapparatus according to claim 4, wherein the pressurising apparatus isconfigured to cycle between the de-pressurising stage and thepressurising stage to facilitate cyclical impact between the first andsecond impact surfaces.
 10. The downhole jarring apparatus according toclaim 2, wherein the pressurising apparatus is configurable in adisabled stage, wherein the pressurising apparatus is prevented fromproviding fluid communication between first and second fluid reservoirs.11. The downhole jarring apparatus according to claim 1, comprising afluid cavity for receiving an actuating fluid.
 12. The downhole jarringapparatus according to claim 11, wherein the pressurising apparatusretains pressure in the cavity during axial separation of the first andsecond impact surfaces.
 13. The downhole jarring apparatus according toclaim 11, wherein the pressurising apparatus is configured todepressurise the cavity to permit the first and second impact surfacesto be impacted together.
 14. The downhole jarring apparatus according toclaim 11, wherein the pressurising apparatus is configured to pressuriseand depressurise the cavity, and wherein the apparatus is reconfigurablebetween: a first configuration in which the first and second impactsurfaces are prevented from impacting each other; a second configurationin which the first and second impact surfaces are subsequently impactedtogether through depressurisation of the cavity; and a thirdconfiguration in which the first and second impact surfaces aresubsequently axially separated through pressurisation of the cavity. 15.The downhole jarring apparatus according to claim 14, wherein theapparatus is configured to cyclically pressurise and depressurise thecavity to permit subsequent impacts between the first and second impactsurfaces.
 16. The downhole jarring apparatus according to claim 1,wherein the rotatable jarring arrangement is configured to receiverotational drive from a rotational drive mechanism.
 17. The downholejarring apparatus according to claim 1, wherein the apparatus isconfigurable from a disabled configuration in which the impact surfacesare prevented from being axially impacted together, and a jarringconfiguration in which the impact surfaces are permitted to be axiallyimpacted together and generate an impact force therebetween.
 18. Thedownhole jarring apparatus according to claim 17, wherein the apparatusis reconfigurable from the jarring configuration to the disabledconfiguration such that the apparatus is re-settable.
 19. A method foruse in jarring an object in a bore, comprising: engaging a downholejarring apparatus according to claim 1 with the object; and applying arotational drive movement to or within the apparatus to cause relativeaxial movement and impact between first and second impact surfaceswithin the jarring apparatus.
 20. A downhole jarring apparatus for usein jarring an object in a bore, comprising: first and second impactsurfaces configured to be axially separated and impacted together togenerate a jarring force; a cavity configured to be pressurised duringaxial separation of the first and second impact surfaces; and arotatable jarring arrangement operable by a rotational drive movement todepressurise the cavity to permit the first and second impact surfaceswhen axially separated to be axially impacted together.